Carburetor



Sept. 15, 1931. M. R. woLFARD CARBURETOR Criginal Filed July 17, 1928lnvenfor. Merl Fi. Wolford Atys.

Patented Sept. 15, 1931 UNITED STATES PATENT OFFICE HERL R. WOLFARD. OFCAMBRIDGE, MASSACHUSETTS, ASSIGNOB TO CHARLES F. HOPE- WELL AND HELEN C.HOPEWELI, A COPARTNEBSHIP DOING BUSINESS AS HOPE- WELL BROTHERS, OFWATERTOWN, MASSACHUSETTS CARBURETOB Original application led July 17,19128, Serial No. 293,371. Divided and this application led July 17,1928. Serial No. 293,372.

This invention relates to improvements in carburetors and the objectthereof is to provide a simple design of mixture-proportioning parts,and regulating means therefor, operable to produce a substantiallyproportional change in the fuel-air ratio during idle and light loadoperation, as well as under heavy load operation.

The present application is a division of my co-pending application,Serial Number 293,- 371 filed July 17, 1928, for improvements incarburetors, in which the preferred embodiment of the inventionrelatesto unit-controlling means for producing a substantially proportionalchange on the fuel-air ratio from idle to fullload and havingcontrolling means operable by changesin temperatures and also preferablyby changes in barometric pressure. In the construction illustrated inthe co-pending application a low flowing head is maintained at the fuelinlet during idle and light load operation of the en 'ne to supplementthe rate of flow induced y the suction head at the metering section .incombination with means producing an uninterrupted flow of mixture fromthe metering section to the engine.

In the present case different specific means are provided formaintaining a continuous flow at a low rate through the fuel inletirrespective of the suction head in the metering section during idle andlight load operation.

An object of the invention, therefore, is to provide means for producinga proper proportioniug of the fuel-air mixture in combination with meansfor maintaining an uninterrupted mixture flow during all normalconditions of operation of the engine from idle to full load.

More particularly the object of the invention is to provide a carburetorconstruction for internal combustion engines comprising a mixing passagehaving a metering section, an inlet section, an outlet section subjectto the suction of the engine, a throttle valve in the outlet section, asuction passage communicating with said inlet section, a fuel inletcommunicating with said suction passage, and in which the suctionpassage leads downwardly from the fuel inlet .to the metering section,

and has a branch intermediate of the fuel inlet and the metering sectioncommunicat-` ing with the outlet section beyond the throttle, providinga combination which is adapted to maintain a continuous anduninterrupted flow of properly proportioned fuel to air mixture to theengine under all normal conditions of operation from idle to full load.

A further object of the invention is to provide a construction of thischaracter comprising a fuel reservoir communicating with the fuel inlet,with means for maintaining with precision a constant fuel level slightlybelow the fuel inlet.

A further object-of the invention is to provide a deviceof'thischaracter with a. valve for controlling Vthe 'fuel inlet having awall com lementary to a portion of the wall of the fuel inlet andchamfered on the opposite side, thus providing a construction which willaccurately regulate the flow of fuel to the suction passage.

A further object of the invention is to provide means for maintainingthe height of fuel in the reservoir slightly below the level of the fuelinlet comprising a valve for regulatin the supply of fuel to thereservoir controlle by float sections symmetrically positioned withrelation to the fuel inlet, with lever mechanism intermediate of thefloat sections and regulating valve operable to transmit a substantiallyconstant multiplied force to the regulating valve regardless of theinclination of the reservoir.

' A further object of the invention is to provide novel means foradjusting the height of the seat for the regulating valve.

A further object of the invention is to provide a carburetorconstruction of the character specified, with means o erable to regulatethe degree of depression elow atmospheric pressure at the fuel inlet.

A further object of the invention is to provide ak simple controllingmeans with thermostatically operable means automatically to regulate thedegree of depression below atmospheric pressure in the lnlet section ofthe mixing passage.

A further object of the invention is to rovide a carburetor of thecharacter speci ed,

with means for admitting hot and cold air, and comprisingthermostatically operable means subject to the temperature of the hotair admitted to the inlet section, and means operable thereby graduallyto diminish the amount of hot air admitted to the inlet section andsimultaneously gradually to increase the amount of cold air admittedthereto.

A further object of the invention is to provide a carburetor of thecharacter specified with means for admitting the fuel-air mixture to themetering section of the mixing passage comprising a transverse slothaving a width less than the normal diameter of the suction passage andgreater in length than said normal diameter of said suction passage.

Another object of the invention is to provide a shield in front of andin proximity to said slot operable to increase the suction head in thesuction passage relative to the suction head in said metering section asthe load increases beyond half load.

These and other objects and features of the invention will more fullyappear from the following description and the accompanying drawings andwill be particularly pointed out in the claims.

In the drawings:

Fig. 1 is a view. mainly in vertical section, of a carburetor containinga preferred embodiment of the invention;

Fig. 2 is a horizontal sectional view of a portion of the constructionillustrated in Fig. 1 on line 2-2 Fig. 1; and,

Fig. 3 is a detail plan view of the means for locking the fuel valvecage in adjusted position.

The preferred embodiment of the invention as illustrated in theaccompanying drawings comprises a casing 1 having an inlet section 2 andan outlet section 3, with an air metering section therebetween ofpredetermined fixed area. As illustrated, an air metering section ofreduced fixed area is formed by providing a filler 5 having a Venturipassage therethrough. A reservoir which is mounted upon. or desirablyformed integrally with the casing, comprises a wall 6 preferablysurrounding a fuel inlet and preferably has a centrallyupwardly-extending boss 7 having a vertical conduit 8 which communicateswith the reservoir through a small orifice 9 having a chamfered wall.The central portion of the boss extends upwardly a short distance abovethe fuel level which is maintained in the reservoir. and the upper endof the 'conduit S desirably is provided with a sleeve forming a fuelinlet 10, the area of which is controlled by a valve 11 which isslidably mounted in said fuel inlet. The peripheral wall 12 of the bossdesirably is of oblong form. as illustrated in crosssection in Fig. 2,and extends upwardly into enga ement with the under face of the cover 13o the reservoir.

A suction passage 14 extends upwardly from the inlet section, thencehorizontally across the fuel inlet and thence downwardly immediately andunobstructedly, and is so branched that one branch l5 communicates withthe outlet passage below the fuel inlet and beyond the throttle 16,while another 'branch 17 continues unobstructedly downwardly andcommunicates with the mixing passage at the air metering section 4thereof. The cover 13 is provided with a downwardly-extending boss 18which is located immediately Aabove the boss 7 and in cooperationtherewith provides a restricted passage 19 forming a metering section'in the suction passage at the fuel inlet 10. Desirably a sleeve 20 isplaced in the portion of the suction passage eyond the metering sectionand is provided with a restricted opening 21 communicating with thebranch 15 of the suction passage which leads to the outlet sectionbeyond the throttle 16. The lower end of the sleeve Q0 desirably extendsthrough the wall of the casin 1 and seats in a recess in the filler 5,therey holding the filler in place. The filler 5 desirably is providedwith a transverse slot 22 which extends through a considerable area ofthe upper wall of the filler 5 and is of a width less than the normaldiameter of the suction passage and of a length greater than saiddiameter. The filler '5 desirably is provided with a segmental boss 23in front of the slot 22 and forms a shield at the end of the suctionpassage which com- K municates with the metering section.

It has been shown experimentally that a shield thus placed in front ofand in proximity to said slot increases the suction head in the suctionpassage relatively to the suction head in the air metering section undercertain operating conditions, thereby increasing the efiiciency and/orthe smoothness of operation of the engine.

The relative increase in fuel delivered to the metering section duringheavy loads as compared with the amount delivered during light loads maybe increased by using series orifices in the fuel inlet conduit. This isparticularly true if orifices are used which have a chamfered inlet,because it is a well demonstrated fact that the discharge coefficient ofsuch orifices increases gradually and very substantially as the suctionhead increases.

ln the embodiment of the invention illustrated herein this isaccomplished by providing the small orifice 9 at the bottom of theconduit 8 with a chamfcred inlet and the fuel inlet 1() with achalnfered valve.

Means are provided for maintaining the liquid level of the fuel in thefuel reservoir slightly below the fuel inlet 10. To accomplish thispurpose fioat sections 24 and 25 are symmetrically disposed relativelyto the fuel inlet 10 and are connected, respectively, to arms 26 and 27of a yoke 28 which is cal passage pivotally mounted upon a pin 29 in ahollow extension 30 of the wall 6 of the fuel reser- V011.

he extension 30 is provide with an upwardly-extending boss 31 which isbored vertically to provide a fuel passage 32 lead` ing to thereservoir. The upper portion of the wall of the bore is Ccrewthreaded toref ceive complementary screw threads of a valve cage 33 which desirablyhas an angular or hexagonal enlargement 34 at. a distance from its upperend. In the preferred onstruction illustrated the cover 13 is' providedwith a V-shaped notch 35 adapted to fit adjacent faces of thehexagonal-enlargement 34 of the valve cage, thereby providing means forlocking the valve `cage from rotation when it has been adjusted at apredetermined height. The upper end portion of the valve cage isprovided with external screw threads 36 toy receive a. coupling 37 forthe end of a supply pi e 38. A valve seat member 39 is interposed)between the coupling 37 andthe upper end of the valve cage 33 andcomprises a head which rests upon the upper end of the valve cage and adownwardly-extending cylindrical portion 40`\\'hich desirably is pressedinto the upper end of the vertical cylindri- 41 of the valve cage. Thevalve member as a. "ertical central bore 42, the lower end of thewall'of which is tapered to form a conical seat complementary to theconical upper end of regulating valve 43 which extends axiallyof thepassage 41 ofthe valve cage and of the bore 42. The lower end of thevalve is provided 'with a. reduced extension 44 which passes through asuit-.able aperture in the yoke 28 in proximity to the pivot 2.9 of saidyoke. The shoulder 45 at the base of the reduced extension 44 desirablyis slightly rounded. The pivot of the yoke 28 is slightly above thepoint of. engagement of the lower end of the `v alve whenthe regulatingvalve isl normally closed.

As heretofore stated, by reason of this construction no sliding contactsare presented which will interfere with the free movement of the valve.Furthermore, the vertical swinging movement of the yoke 28,even thoughslight, transmits a suflcient lateral movement to the lower end ofthevalve 43 which will prevent the sticking of the valve upon its seat. Thedistance between the fulcrum of the yoke and the point ofengagementtherewith by the valve 43 must be so short relatively to the distancefromthe point of engagement to the vertical plane ,of the horizontalaxisof the float sections 24 and 25, that a sutliciently large andvsubstantially constant multi lied leverage' is interposed between theoat sections and the regulating valve which will maintainthe liquidlevel in the reservoir with only small variations in height slightlybelow the -fuel inlet during idle and light load operation of theengine.

This multiplied levera e necessitates a substantial drop in the positionof the float sections, (about when the engine is operating at full load,in order to permit asuficient amount of fuel to flow into the reservoir.By reason of the -adjustability of the valve cage 33 within the boss 31the vertical position of the valve seat may be varied to establish aliquidlevel in the reservbir ac' curately at a predetermined heightvslightly below the fuel inlet 10. In' this construction the valvecagewill be locked in adjusted position whenthe cover'13 vofthereservoir is placed in position upon the top of the reservoir andsecured thereupon by suitable screws. I A,

The effective area of thefueloutlet is regulated ,by the valve 11 whichdesirably is of cylindrical `fo'rnislidably mounted in a bearing in theboss 18 and extending across the metering section 19 of the suctionpassage into the fuel inlet 10. v

The lower endfof the valve is chamfered, preferably on the down-streamside, to present a flat face 46V extending at an acute angle to the axisofthe valve. Preferably butnot neessarily, the sleeve 47 isforced intothe upper end ofthe Iinlet conduit 8 andthe inner wall of thesleeve iscom' lementary to'l a poi-tien, 'preferably the cy indiical upstreamwall, ofthe valve 11. The effective area of the fuel outlet may bevaried as required by vertical adjustment of Vthe valve. .A

Any suitable means may be provided for adjusting the valve 11. In theconstruction illustrated adjusting means are l provided which also actto maintain a portion of the wall of the valve 11 continuously in enagement with thecomplementar wall o the sleeve 47 forming the fuel `inet.

In the Aconstruction illustrated, a spiral spring 48, which is seated uon the cover surrounds the valve 11 and a uts at its upper end against ashoulder on the under side of an enlarged section 49 .of the valve. Aplate 50 is clamped upon the upper face of the .enlarged portion of thevalve b a nut 51. The platel 50 is engaged by the liead of an adjustingscrew 52 which is located in proximity to the valve 11 and inparallelism therewith and engages a screw-threaded aperture in the boss53 u` on the cover. By reason of this construction a leverage is exertedby the spring 48 against the head of the adjusting screw 52, whichmaintains the cylindrical portion of the valve in constant engagementwith the complementary wall of the inlet. Y

In the normal operation of the invention as above described, during theidle operation of the engine, with the throttle valve 16 inapproximately closed position, as illustrated in Fig. 1, the suctionofthe engine produces -a partial vacuum in the branch 15 of the suctionpassage, thereby causing air to flow through the metering section 19 ofthe suction passage, thus inducing a flow of fuel through the inlet 10which mixes with the air in the suction passage and passes through .therestricted -aperture 21 and branch 15 to the engine.- During such idleoperation air is also caused to flow upwardly through the slot 22 in thefiller 5 into the lower end of the branch 17 of the suction passage andout through the restricted aperture 21 to mingle with the fuel-airmixture drawn through the suction passage.

The area of the restricted Apassage* 21 in the sleeve 20 is soproportioned, relativel to the area of the lower end of the branc 17leading to the air metering section 4 the mixing passage and to theareav of the metering section 19 of the suction passage, that thesuction produced in the metering section 19 will maintain a flow of fuelfrom the fuel inlet at a low flowing head sufficient to producesatisfactory operation on idle.

It is well known that when air is drawn through an orifice of restrictedarea, such as the aperture 21,.a maximum flow through that orifice willbe induced when the pressure in the passage 15 is reduced toapproximately fifty-three per centv of the absolute pressure existing atthe entrance tothe orilice. However, when fuel is `entrained in the airdrawn through such orifice, this limiting flow will be reached at asomewhat lower absolute pressure inthe passage 15, but in an case theflow through theorifice 21 will fie constant during a considerableperiod of operation as the throttle valve is gradually opened from idle.By reason of this fact a low flowing head is continuously maintained atthe fuel inletirrespective of the suction head in the air meteringsection 4 of the mixing passage during idle and light load operation upto about half load.

The flow of air through the slot 22. from the metering section of themixing passage toward the aperture 21 will be gradually reduced as thethrottle valve is opened, and

a positive downward flow of fuel-air mixture will be induced through theslot 22 into the metering section 4 of the mixing passage.

As the suction head in the air metering section 4 of the mixing passageincreases, a gradual lessening of flow toward the restricted opening 21is produced. Then a gradually increasing positive flow downwardlythrough the slot 22 is produced which builds up gradually from idle anincreased suction at the metering section 19 of the suction passage,thus inducing a greater flow of fuel from the fuel inlet 10. By reasonof this construction the mixture flow is continuous and'unobstructedfrom the metering section of the suction passage and therebeyond.

Beyond half open throttle the suction head in the suction passage 15will gradually decrease, thereby decreasing the flow through the opening21. However, the low fiowing head previously referred to is ofrelatively small importance in the range of operation beyond half openthrottle, for the reason that' the suction head in the air meteringsection 4 of the mixing passage is such as to produce a suction head inthe metering section 19 of the suction passage which is many timesgreater than the low flowing head previously referred to. For example,lat and beyond half load the suction head in the metering section of thesuction passage would normally be fourV idle to full -load of theengine, to change the' ratio of fuel to air supplied to the mixingpassage and in conjunction with mechanism arranged to maintainuninterrupted mixture flow fromy beyond said fuel inlet.- In the presentembodiment of the invention this is accomplished by regula-tingthetsuction head at the fuel inle In the particular construction illusfn;ated,v .a choke valve-or valves for controlling the admissio'r/ of airinto the inlet section of the metering passage is or are provided.Obviously when the choke valve or valves is or are in partially closedposition the suction in the inlet section is much greater than when thechoke valve or valves is or are more widely open. Obviously the suctionAhead applied to the inlet section will increase proportionally thesuction head at the metering section 4 of the mixing passage and atthealr metering section 19 of the suction passage. By controlling theadmission of air into the inlet section of .the suction passage,therefore, the degree of depression below atmospheric pressure in thesuction passage may be regulated, and such regulation in thepresentponstruction will increase proportionally the suction head at theair metering section 4 of the mixing passage and also the suction headat the.l

metering sect-ion 19 ofthe suction passage, thus enabling a regulatingmeans to be employed which will be operable to change the ratio of fuelto air supplied to the mixing chamber in conjunction withmeans'heretofore described, which is operable to maintain uninterruptedmixture flow from beyond said fuel inlet. Such regulating means may alsocomprise a thermostatic device operable to regulate the degree ofdepression below atmospheric pressurev in the metering Sectionl until apredetermined temperature is reached,

and thereafter operable gradually to diminish the amount of hot airadmitted to the inlet section and simultaneously gradually to increasethe amount of cold air admitted thereto, in the manner above described.

In the preferred construction illustrated herein means are provided forsupplying both and cold air to the inlet section of the carburetor withthermostatically-controlled valves operable to vary the suction head inthe inlet section during the Warming up of the engine until normaloperating temperatures are obtained, and thereafter operable to varygradually the relative proportions of hot and cold air to maintain theair admitted to the mixing passage at a proper tem erature.

T is may be readily accomplished by connecting to the fuel inlet sectiona thermostatic control for carburetors of the type disclosed in my priorPatent No. 1,627 ,947 granted May 10, 1927. This carburetor controlcomprises a tubular T-shaped casing 54, one of the branches 55 of whichis telescopically mounted in and secured to the inlet end of the inlet`section 2, with the other branch 56 forming the cold air inletextending in the opposite direction. The hot air in et branch 57preferably extends at right angles to the branches 55' and 56 and isadapted to be connected to a usual stove, such as conduit surroundingthe exhaust mani- The means for chokin preferablycomprises a termostatically-operated valve 58 of the character described in thepatent aforesaid, which, upon cold starting, is located approximately 1nthe choking position illustrated in Fig. 1. The construction andoperation lof this thermostaticvalve is such that, as the en ine fwarmsup, the thermostat will gradua ly rotate the valve in a clockwisedirection toward open position and, as thefhot air from theengineincreases beyond a predetermined amount, will rotate the valvebeyond vertical positlon, so that it will act radually again to chokethe admission of ot air.

The thermostatically-operable valve 58 has connected to it an arm 59which is connected by a link 60 to an arm 61, which in turn is connectedto the shaft 62 of a choke valve 63 in a cold air inlet. The arrangementof the arms 59, 61 and the link 60 is such that the initial o ning ofthe thermostatically-controlled c oke valve 58, during cold startin andwarming of the engine, has but little e ect upon the opening of the coldair valve 63, but as the thermostatically-operable choke valve 58 ymovesthrough and beyond vertical position the cold air valve 63 is movedtoward open position with relatively increasing rapidity.

Desirably the shaft 64 of the tnermostatic valve is extended through thewall of the the hot vair inlet branch 57 and is provided with an arm 65the end of which is connected to a rod 66 leading to theinstrument-board of the automobile, thereby providing manual means forrotating the thermostatic choke valve further toward closed positionthan that which it normally assumes under the action of the thermostat,to increase the depression in the mixing" passage and suction passageupon cold starting of the engine. Y

In the operation of the device, therefore, the operator may move thethermostatic choke valve of the hot air inlet to such choking positionas to produce a suction head upon the fuel inlet l0 sufficiently tosuppl the desired increased amount of fuel for cold starting. Suchmanual choking mechanism may be immediately released upon the startingof the engine. Thereafter' the proper suction head will be maintained bythe action of the thermostat during the warming-up period of the engine,and also during atmospheric changes in temperature.

By reason of this construction a carburetor for an internal combustionengine is provided comprising a mixing passage having a meteringsection, means for controllin the How through the mixing passage, a fuelInlet communicating with said metering section and subject to a suctionhead substantially proportional to the suction head at the meterinsection, with means for delivering fue through said fuel inletcontinuously at a low, predetermined rate during idle and light loadoperationin addition to the suction head in the metering section,co-ordinated with said mixing passage in such a manner as to produceuninterrupted mixture flow from said fuel inlet and therebeyond incombination with regulating means acting on a single fuel inlet tochange the ratio of fuel to air supplied to the mixing passage, asdistinguished from prior constructions, in which a plurality of passagesfor the fuel or the fuel-air mixture are provided which necessitatecomplicated controlling mechanism and which cause an interrupted orreversal of flow through certain of said passages, with a consequenterratic variation in the proportion of fuel to air delivered to theengine at some point in the load range of operation of the engine,thereby decreasing the efficiency of the engine, causing a wastage offuel and precluding the smoothness of operation of the engine obtainedby the present invention.

It will be understood that the particular embodiment of the inventiondisclosedherein is of an illustrative character and is not restrictiveof the meaning and scope of the following claims.

Having thus described the invention, what is claimed as new, and desiredto be secured by Letters Patent, is:

1. A carburetor for an internal combustion engine comprising a mixingpassage having a metering section, an inlet section, an outlet sectionsubject to the suction of the engine, a throttle valve in said outletsection, a suction passage havin a fuel inlet and leading downwardlythere rom to said metering section and having a branch intermediate ofsaid f-uel inlet and said metering section communieating with saidoutlet section beyond said throttle, a valve slidably mounted in saidfuel inlet having a wall complementary to a portion of the wall of saidfuel inlet and chamfered on the opposite side, and means for maintainingsaid complementary walls in contact.

2. A carburetor for an internal combustion engine comprising a mixingpassage having a metering section, an inlet section, an outlet sectionsubject to the suction of the engine, a throttle valve in said outletsection, a suction passa e havin a fuel inlet and leading downward ythere rom to said metering section and having a branch intermediate ofsaid fuel inlet and said metering section communicating with said outletsection beyond said throttle, a valve slidably mounted in said fuelinlet having a wall complementary to a portion of the wall of said fuelinlet and chamfered on the opposite side, and means for adjusting saidvalve having means for maintaining said complementary walls in contact.

3. A carburetor for an internal combustion engine comprising a mixingpassage having a metering section, an inlet section, an outlet sectionsubject to the suction of the engine, a throttle valve in said outletsection, a suction passage communicating with said inlet section havinga fuel inlet and leading downwardly therefrom to said metering sectionand havin a branch of restricted area intermediate osaid fuel inlet andsaid metering section communicating with said outlet section beyond saidthrottle valve, said suction passage being unrestricted beyond said fuelinlet and adapted to permit uninterrupted mixture flow at all times fromsaid fuel inlet to said mixing passage, a fuel reservoir sur roundinsaid fuel inlet and communicating therewit means for supplying fuel tosaid reservoir including a. regulating valve, float sectionssymmetrically positioned with relation to said fuel inlet, levermechanism intermediate of said float sections and said regulating valveoperable to transmit a sufliciently large and substantially constantmultiplied force to said regulating valve regardless of the inclinationof the reservoir ,thereby to maintain the liquid level in said reservoirwith only small variations in height slightly below said fuel inletduring idle and light load operation of the engine.

4. A carburetor for an internal combustion engine comprising a mixingpassage having a metering section, an inlet section, an outlet sectionsubject to the suction of the engine,

a throttle valve in said outlet section, a suction passage communicatingwith said inlet section, a fuel inlet communicating therewith, saidsuction passage leading downwardly therefrom to said metering sectionand havin a branch of restricted area intermediate o said fuel inlet andsaid metering section communicating with said outlet section beyond saidthrottle valve, said suction passage being unrestricted beyond said fuelinlet and adapted to permit uninterrupted mixture flow at all times fromsaid fuel inlet to said mixing passage, a fuel reservoir surroundingsaid fuel inlet and communicating therewith, means for supplying fuelrtosaid reservoir including a regulating valve, iioat sectionssymmetrically positioned with relation to said fuel inlet, levermechanism intermediate of said float sections and said valve operable totransmit a sufficiently large and substantially constant multipliedforce to said regulating valve regardless of the inclination of thereservoir thereby to maintain the liquid level in said reservoir, withonly small variations in height, slightly below said fuel inlet duringidle and light load operation of the engine, a valve seat for saidvalve, and means for adjusting the height of said valve seat to tix theliquid level of the fuel in said reservoir relatively to said fueloutlet.

5. A carburetor for an internal combustion engine comprising a mixingpassage having a meterinU section, an inlet section, an outlet sectionsu ject to the suction of the engine, a throttle valve in said outletsection, a suction passage communicating with said inlet section, a fuelinlet communicating therewith, said suction passage leading downwardlyfrom the fuel inlet to said metering section and having a branch ofrestricted area intermediate of said fuel inlet and said meteringsection communicating with said outlet section below said fuel inlet andbeyond said throttle valve, said suction passage being unrestrictedbeyond said fuel inlet and adapted to permit uninterrupted mixture flowat all times from said fuel inlet to said mixing passage, and meansoperable to regulate the degree of depression below atmospheric pressureat said fuel inlet.

6. A carburetor for an internal combustion engine comprising a mixingpassage having a metering section, an inlet section, an outlet sectionsubject to the suction of the engine, a throttle valve in said outletsection, a suction passage communicating with said inlet section havinga fuel inlet and leading downwardly from the fuel inlet to said meteringsection and having a branch of restricted area intermediate of said fuelinlet and said metering section communicating with said outlet sectionbelow said fuel inlet and beyond said throttle valve, said suctionpassage being unrestricted beyond said fuel inlet and adapted to permituninterrupted mixture flow at all tlmes from said fuel inlet to saidmixing passage, and regulating means including a thermostatic deviceoperable to regulate the degree of de ression below atmospheric ressurein sai inlet section.

7. A car uretor for an internal combustion engine comprising a mixingpassa ge. h lving a metering section, an inlet section, r leans foradmitting respectively hot and c ld air thereto, an outlet sectionsubject to the suction of the engine, a throttle valve in said outletsection, a suction passage communicating with said inlet section havinga fuel inlet and leading downwardly from the fuel inlet to said meteringsection and havin a branch of restricted area intermediate o said fuelinlet and said metering section communicating with said outlet sectionbelow said fuel inlet and beyond said throttle valve, said suctionpassage bein unrestricted beyond said fuel inlet and a apted to permituninterrupted mixture How at all times from said fuel inlet to saidmixing passage, and regulating means, including a t ermostatic devlce,subject to the temperature of the hot airadmitted to said inlet section,and means operable thereby to regulate the degree of de- Ipression belowatmos heric ressure in said metering section unt a pre eterminedtemperature is reached and operable thereafter graduall t0 diminlsh theyamount of hot air admitte to said inlet section and simultaneously toincrease the amount of cold air admitted thereto.

8. A carburetor for an internal combustion engine comprising a mixingpassage having a meterin section, an inlet section, an outlet sectionsubject to the suction of the engine, a throttle valve in said outletsection, a suction passage, a fuel inlet communicating therewith, saidsuction passage leading downwardly therefrom to said metering sectionand communicating therewith through a transverse slot having a lengthgreater than the normal diameter of the suction passage and having abranch intermediate of said fuel inlet and said slot communicating withsaid inlet section beyond said throttle, said suction passage beinunrestricted beyond said fuel inlet and a apted to permit uninterruptedmixture fiow at all times from said fuel inlet to said mixing passage,and a shield in front of and in proximity to said slot operable toincrease the suction head in said suction passage relatiavely tothesuction head in the air metering section under certain operatingconditions.

9. A carburetor for an internal combustion engine comprising a mixingpassage having a metering section, an inlet section, an outlet sectionsubject to the suction of the engine, a throttle valve in said outletsection, a suction passage communicating with said inlet section havinga fuel inlet and leading downwardly therefrom to said metering sectionand havin a branch of restricted area intermediate o? said fuel inletand said metering section communicating with said outlet section beyondsaid throttle valve, a fuel reservoir surrounding said fuel inlet andcommunicating therewith through a small orifice with a chamfered inletleading to the conduit of said fuel inlet, a valve slidably mounted insaid fuel inlet having a wall complementary to a portion of t e wall ofsaid fuel inlet and chamfered on the opposite side, and means formaintaining the complementary walls in contact.

In testimony whereof, I have signed my name to this specification.

MERL R. WOLFARD.

